342
FXUS65 KBYZ 100658
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
1258 AM MDT SAT OCT 10 2026
KEY MESSAGES
- COLD FRONT ARRIVES EARLY TODAY, THEN MUCH COOLER TONIGHT THROUGH
MONDAY. MANY LOCATIONS COULD SEE THEIR FIRST FREEZE OF THE
SEASON SUNDAY NIGHT OR MONDAY NIGHT.
- STRONG WEATHER SYSTEM MOVES INTO REGION THIS WEEKEND. SNOW
ACCUMULATION IS LIKELY SATURDAY NIGHT TO MONDAY FOR THE WESTERN
MOUNTAINS AND FOOTHILLS, WITH RAIN AND SOME WET SNOW AT LOWER
ELEVATIONS, MAINLY WEST OF ROSEBUD COUNTY. POTENTIAL IMPACTS TO
TRAVEL AND OUTDOOR RECREATION.
- WEATHER PATTERN REMAINS UNSETTLED THROUGH MUCH OF NEXT WEEK.
DISCUSSION
THROUGH NEXT FRIDAY...
EARLY MORNING COLD FRONT WILL FINALLY RID US OF THE HOT & DRY AIR
MASS WE HAVE DEALT WITH FOR MOST OF THE PAST WEEK. STILL NEED TO
WATCH FOR PERIODIC DOWNSLOPE GUSTS ALONG EASTERN SLOPES OF THE
MOUNTAINS UNTIL THE FROPA, WHICH SHOULD OCCUR OVER THE SOUTHERN
FOOTHILLS IN THE 12-15Z TIME FRAME. POST-FRONTAL N-E WINDS WILL
BRING A MUCH COOLER DAY WITH TEMPS IN THE 50S IN THE NW TO MID 70S
IN THE S/SE. COLD ADVECTION INCREASES AGAIN THIS EVENING AND WIND
GUSTS WILL BE STRONGER, AS TEMPS FALL TO THE 30S TO LOWER 40S.
SHOWER POTENTIAL INCREASES OVER THE WEST TODAY, AND CANNOT RULE
OUT A FEW WEAK T-STORMS IN THE SOUTH IN THE AFTERNOON, OTHERWISE
THE MAIN SHOW BEGINS TONIGHT AS AN UPPER LOW DROPS THRU THE PACNW
AND A VERY MOIST SW FLOW OVERRUNS THE DEEPENING COOL AIR ON OUR
SIDE OF THE MOUNTAINS.
AS CONFIDENCE HAS INCREASED FOR ACCUMULATING SNOW OVER WESTERN
MOUNTAINS AND FOOTHILLS HAVE ALREADY ISSUED WINTER HIGHLIGHTS FOR
THESE AREAS. CONFIDENCE HAS ALSO INCREASED THAT EASTERN ZONES,
ESPECIALLY ROSEBUD COUNTY EASTWARD, WILL REMAIN TOO WARM FOR
ANYTHING BUT RAIN, WITH LOWER PRECIP AMOUNTS OVERALL THAN FURTHER
WEST. THESE TRENDS ARE DUE TO THE FACT THAT THE PACNW LOW WILL
TRACK SOUTHWARD NEAR THE COAST. NOT ONLY DOES THIS KEEP THE
BOUNDARY LAYER OVER THE EAST WARMER (STRONGEST PRESSURE RISES/COLD
ADVECTION DROPS FROM CANADA THRU CENTRAL MT), BUT THE TRACK OF
MOISTURE FROM FORMER HURRICANE RACHEL WILL TRACK THRU CENTRAL MT
RATHER THAN BE SHUNTED TO THE EAST. PRECIP FORECAST HAS BEEN
ADJUSTED ACCORDINGLY, WITH 1-2" WEST OF BILLINGS (GREATEST OVER
MOUNTAINS), 0.40-0.80" ACROSS THE NORTHEAST, AND ONLY 0.10-0.40"
FOR THE SOUTHEAST.
SURGE OF MOISTURE FROM RACHEL IS EXPECTED TO PUSH PWATS TO NEAR AN
INCH, REMARKABLE FOR OCTOBER AND 200% OR MORE OF NORMAL. IF THE
AIR MASS WERE SLIGHTLY COLDER WE'D BE LOOKING AT A MAJOR WINTER
STORM, BUT AS IT IS THE SURFACE TEMPS WILL HOLD BACK SNOW
ACCUMULATIONS QUITE A BIT, ESPECIALLY DURING THE DAYTIME HOURS.
THE TOUGHEST FORECAST AT THIS TIME SEEMS TO BE IN THE AREA EAST OF
THE WESTERN FOOTHILLS AND WEST OF ROSEBUD COUNTY, WHERE RAIN
SHOULD BE DOMINANT AND ANY SNOW ACCUMULATION WILL BE ELEVATION
DEPENDENT AND MAY BE LIMITED TO ONLY THE HIGHER HILLS. THAT SAID,
THE MOISTURE SURGE SUNDAY NIGHT INTO MONDAY MAY BE THE GREATEST
OPPORTUNITY FOR THIS AREA TO SEE WET SNOWFALL, AND THIS INCLUDES
THE CITY OF BILLINGS. THE CHANCE OF AN INCH OF SNOW AT BILLINGS
REMAINS LOW AT 20% BUT CONTINUE TO STRESS THE UNCERTAINTY. THE
RISK OF AT LEAST A FOOT OF SNOW OVER THE WESTERN MOUNTAINS IS
60-80% ABOVE 8KFT. THIS IS AN INTERESTING SETUP AS EVEN THE
BIGHORNS WILL STRUGGLE TO SEE SNOWFALL WITH SNOW LEVELS OF 9-10KFT
ACROSS N/NE WYOMING.
THERE IS EMERGING STRONG CONSENSUS THAT ONCE THE RACHEL MOISTURE
EXITS MONDAY THE WESTERN LOW WILL CUT OFF AND WE WILL SEE DRYING.
MONDAY WILL REMAIN CHILLY AND THERE IS A HIGH RISK OF A FREEZE
OVER MUCH OF THE REGION MONDAY NIGHT (FOR THOSE AREAS THAT REMAIN
TOO WARM DURING THE SYSTEM ITSELF).
AFTER CHILLY DAYS SUNDAY & MONDAY (HIGHS IN MID 30S TO MID 40S),
TUESDAY SHOULD BE DRY AND WARMER WITH TEMPS BACK TO THE 50S. THE
CUT OFF LOW OVER THE SW IS EXPECTED TO LIFT TO THE NORTHEAST AND
BRING MAINLY THE EAST A CHANCE OF RAIN SHOWERS WEDNESDAY. WE'LL
HAVE TO SEE ABOUT A CANADIAN CLIPPER INTO THURSDAY AS ALL MODELS
HAVE TRENDED WEAKER, BUT THERE IS A LOW CHANCE OF RAIN/SNOW
SHOWERS IN THE EAST AND SOUTHERN UPSLOPE AREAS, ALONG WITH BREEZY
NW WINDS. FRIDAY IS LOOKING QUIET, BUT PERHAPS STILL COOL IF THE
UPPER RIDGE AXIS STAYS TO OUR WEST FOR ANOTHER DAY. GENERALLY
SPEAKING LOOK FOR HIGH TEMPS IN THE 50S TO LOWER 60S THROUGH THE
2ND HALF OF THE WORK WEEK.
LOOKING FURTHER AHEAD, THERE IS GROWING CONFIDENCE FOR A BUILDING
RIDGE AND RETURN OF WARMER THAN NORMAL TEMPS NEXT WEEKEND.
JKL
AVIATION
06S TAF AND AVIATION DISCUSSION...A PREFRONTAL TROF WILL MOVE
THROUGH THE AREA OVERNIGHT SHIFTING WINDS TO A GENERALLY LIGHT
NORTH/NORTHEAST DIRECTION BEFORE SUNRISE. JUST AHEAD OF THE TROF
PASSAGE, DOWNSLOPE WESTERLY WINDS WILL GET GUSTY (25-35KTS)
ACROSS SOUTHERN FOOTHILLS ZONES INCLUDING KSHR. THESE GUSTS WILL
DIMINISH BEHIND THE WIND SHIFT. AROUND SUNRISE ISOLATED SHOWERS
WILL DEVELOP OVER THE WESTERN FOOTHILLS (KLVM) SHIFTING FURTHER
EAST TOWARD KBIL BY LATE MORNING. MAIN COLD FRONT WILL MOVE IN
FROM THE NORTH DURING THE AFTERNOON HOURS, DROPPING THROUGH THE
SHERIDAN COUNTY BY EARLY EVENING. EXPECT INCREASED SHOWER ACTIVITY
ALONG THE FRONT AS IT MOVES THROUGH, AND AN ISOLATED THUNDERSTORM
CAN'T BE RULED OUT. OVER THE WESTERN FOOTHILLS WINDS TURN
EASTERLY AND GET GUSTY. THIS WILL BRING ENHANCED UPSLOPE
PRECIPITATION LATE AFTERNOON INTO THE EVENING HOURS WITH LOCALLY
HEAVY SHOWERS DROPPING FLIGHT CONDITIONS TO IFR LEVELS AT TIMES.
AFTER 06Z SUNDAY SHOWERS WILL CONSOLIDATE INTO MORE PERSISTENT
RAIN OVER THE WESTERN HALF OF THE FORECAST AREA, WITH SNOW LEVELS
DROPPING TO UNDER 6KFT AGL FOR THE WESTERN MOUNTAINS AND
FOOTHILLS. CHAMBERS
PRELIMINARY POINT TEMP/POPS
TDY SUN MON TUE WED THU FRI
-------------------------------------------------------
BIL 064 037/042 032/042 031/052 036/058 039/058 036/062
2/W ++/O +7/O 11/B 12/W 22/W 10/U
LVM 064 030/038 027/043 025/052 027/055 029/057 028/064
9/T ++/O +6/S 11/B 11/U 22/W 10/U
HDN 069 038/047 033/045 030/055 034/059 036/060 031/064
2/W 9+/R +8/O 11/B 23/W 32/W 10/U
MLS 069 040/048 035/044 032/055 038/058 039/057 034/059
0/B 8+/R +9/O 11/B 12/W 32/W 10/U
4BQ 073 043/051 040/048 034/057 041/058 041/057 036/060
0/U 48/R +7/R 12/W 35/W 43/W 21/U
BHK 075 035/050 030/046 029/055 033/059 034/057 030/058
0/U 38/R +9/R 21/B 23/W 43/W 21/U
SHR 073 037/049 034/047 029/055 033/057 034/057 030/062
2/W 89/R +5/R 22/W 55/W 54/W 21/U
BYZ WATCHES/WARNINGS/ADVISORIES
MT...WINTER WEATHER ADVISORY IN EFFECT FROM MIDNIGHT TONIGHT TO
NOON MDT MONDAY FOR ZONES 40-63-65-66-141-228.
WINTER STORM WARNING IN EFFECT FROM 6 PM THIS EVENING TO NOON
MDT MONDAY FOR ZONES 67-68.
WINTER STORM WARNING IN EFFECT FROM MIDNIGHT TONIGHT TO NOON
MDT MONDAY FOR ZONE 172.
WY...NONE.
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